The present invention relates generally to improvements in ordnance and more particularly to the construction of warhead cases and missile mainframe members.
In the prior art, most missile fragmentation warheads either use a solid steel case filled with explosive (which is the conventional design) or consist of explosive surrounded by a thin shell with "discrete" fragments glued to the shell, which is generally called the discrete fragment design. In either case the warhead is then mounted into the ordnance section where structural loads are carried by a surrounding shroud.
An example of the conventional steel case design is LaRocca, U.S. Pat. No. 3,799,054 filed Mar. 26, 1974. This reference teaches a warhead for controlling the fragmentation of explosive devices having a cylindrical metallic fragmentation casing, wrapped with metallic strips of heavy density to cause fragments to form. This type of construction employs heavy construction materials which, by necessity, must be massive in areas that optimum airframe design would dictate a lighter or different design. This conventional warhead highlights the design tension between fragmentation and structural integrity. Generally a missile airframe demands light, strong materials, and warhead fragments need to be heavy, close tolerance objects. Methods for achieving uniform fragmentation are generally not consistent with good airframe design.
The second standard type of ordnance case construction, the discrete fragment design is represented by Brumfield et al., U.S. Pat. No. 3,977,327 filed Aug. 31, 1976. The Brumfield et al. reference is typical of many fragmentation schemes which precut fragments and then must sandwich them between steel or aluminum cylinders to form the case. The required airframe structure is then parasitic weight from a warhead design perspective.
In a like manner, both the discrete fragment and the conventional design share a common flaw from the overall system perspective. In both designs the warhead is usually carried as parasitic weight within a surrounding missile shroud. There are two drawbacks to this. First, the warhead is forced to "blow" through the shroud. Having to do this degrades fragment breakup as well as fragment velocity. Second, to minimize fragment degradation the missile shroud is made as thin and light as possible in the blow through area thereby reducing the shroud's structural integrity.
This parasitic weight issue can be alleviated to some degree by utilizing an integral warhead with a removable explosive assembly. However, this option suffers from an inability to customize fragmentation and from a weight penalty caused by using a steel shroud.
The problem of parasitic weight is attenuated by Applicants' invention entitled "Filamentary Composite Dual Wall Discrete Fragment Warhead," Ser. No. 07/740,522 filed even date with this application. While considered nonessential to the claims of this application, the Dual Wall Warhead might be the warhead of choice in smaller missiles. Likewise, there are many design choice fragmentation techniques available to the designing technician. One such device suitable for constructing a fragmentation panel which might be used with the present ordnance section is shown in Applicants' copending application Ser. No. 07/740,524, entitled "Fragmenting Notched Rod for Warheads" filed even date with this application. The teachings of this application, while also considered nonessential to the claims appended hereto, provide a general description of one of many possible fragmentation panels. Another possible fragmentation panel might be constructed of composite fragmenting rods, taught in Applicants' copending application entitled "Composite Fragmenting Rods for Warheads," Ser. No. 07/740,528, also filed even date with this application. The teachings of this application are likewise nonessential to the claims appended hereto.
Another recent concern in the warhead arts is the development of warheads that are safe to carry on our nation's ships and aircraft. These concerns are reflected in the new insensitive munitions requirements which became effective for all naval munitions in 1987. One of these requirements is that a warhead survive a fire or high heat environment without exploding. The steel or metallic case warheads do not allow the venting necessary so that the explosive mix burns rather than explodes. Elaborate cook-off plugs and other schemes to allow venting further degrade the case integrity and further reduce strength.
The disadvantages of the conventional design and the discrete fragment design are overcome by the present invention which provides a lightweight, easily manufactured missile mainframe member which will also integrate the warhead and any associated electronics.